This application claims the priority of PCT application PCT/CH98/00397, filed Sep. 16, 1998, and of Swiss application 2258/97, filed Sep. 25, 1997, both of which are incorporated herein by reference.
The invention relates to a device for delivering an injectable product including an acoustic or vibrational sensing unit as set forth in the preamble of claim 1.
Devices like those of the invention preferably concern delivery devices for injecting or infusing a liquid solution of an active substance, preferably a liquid medicament. In particular it is preferred that such devices relate to portable devices, especially in the form of so-called injection pens always referred to in the following representative for others.
Injection pens as known, for example, from WO 93/16740, but also pumping devices, as known for example from EP-B-0 143 895, for infusing or injecting/infusing solutions of active substances comprise a housing in which a container, containing the product, can be accommodated in an accommodation provided for this purpose. Shiftingly mounted in the container is a piston. When the piston is urged in the delivery direction a dose of the product is dispensed, due to it being displaced by the piston. For this purpose, the container, generally an ampule, is fixed in the accommodation such that a driven member of a delivery mechanism urges the piston in forward direction to deliver the product. The delivery mechanism comprises substantially two elements, the aforementioned driven member and a drive means. The driven member protrudes into the containerxe2x80x94in the direction of the pistonxe2x80x94when the container is accommodated in the housing. The drive means engages the driven member in such a way that actuation of the drive means urges the driven member in the delivery direction. In known injection pens having spindle drives the drive means is actuated both by rotation, namely for the purpose of dispensing,the product dose to be delivered by the next injection, and also by a linear shift in the delivery direction of the piston, namely by a manually exerted pressure. However, also conceivable is a delivery mechanism whose driven member comprises a saw tooth structure and the drive means is equipped with the corresponding mating elements. In known pumping devices, having spindle drives and operated by electric motors, the drive means is actuated only by rotation. This rotation prompts, in turn, an advancement of the driven member in forward direction which, however, in pumping devices is generally translated directly to the piston.
The liquid solution of the active substance is discharged through a cannula mounted on the injection pen. The rear end of the cannula flowingly communicates with the active substance solution while the front end protrudes from the injection pen and can pierce the skin. In pumping devices, the cannula is located at the end of an infusion tube opposite the pump.
For administering the active substance solution the cannula is first pushed into the skin and, subsequently, the active substance solution is dispensed via the cannula into the body either by manual or motor driven actuation of the delivery mechanism. Dispensing occurs such that, upon actuation of the delivery mechanism, the piston is shifted by a certain travel in the direction of the ampule orifice, as a result of which first a relatively large amount of active substance is dispensed and, subsequently, during a relatively short time interval, the active substance is delivered only in droplets droplets through the cannula. However, where highly concentrated solutions of active substance are concerned, this last dribble is not to be ignored. This is why the patient is requested, after having actuated the delivery mechanism, to leave the cannula in place hypodermically for 5 to 10 seconds so that these last droplets likewise enter the body. It is often the case, however, that the patient lacks the necessary timing and removes the cannula prematurely.
Known from WO 97/30742 is an apparatus which solves the above problem by incorporating an electronic display. However, this fails to be convincing since users, in particular users of insulin delivery devices, often suffer from impaired vision and thus visual displays are rather unfortunate. In addition to this, visual displays in apparatuses in use are a nuisance since they always require that the patient, while using the apparatus, has a good view of the display.
This is where the invention provides a solution. The invention is based on the object of creating a device for delivering a product dose which alerts the patient to remove the cannula from the skin by emitting an acoustic signal or by means of vibration.
The invention achieves the above object with a device comprising the features as set forth in claim 1.
The advantages attained by the invention are substantially to be appreciated in that the acoustic signal or vibration alerts the patient in a simple manner to the fact that the last droplets of an injection/infusion have entered the body and that, thus, the cannula can be removed from the body.